1. Field of the Invention
The present invention relates to the control of switched reluctance machines and, particularly, those machines which are used as a prime mover in a translation system including transport systems.
2. Description of Related Art
The present invention relates generally to transportation systems utilizing electromagnetic propulsion, and more particularly to a transportation system utilizing linear switched reluctance propulsion.
As world population rises and urban areas become increasingly congested, the need for fast, reliable, energy-efficient and environmentally-friendly mass transportation becomes ever more urgent.
Transportation using electromagnetic propulsion is known. For example, magnetic levitation (mag-lev) systems are used in trains and similar forms of transportation. Benefits offered by mag-lev include a smooth, quiet ride at high speeds, with little mechanical wear on supporting infrastructure, since the systems are contactless and therefore frictionless. Mag-lev also tends to be energy-efficient and having a smaller environmental impact than conventional rail systems, due in part to the fact that pollutants are not generated.
However, drawbacks exist with known mag-lev systems. For example, separate electromagnetic arrangements are used for lift and propulsion. That is, known mag-lev systems typically employ a combination of superconducting magnets, permanent magnets or more conventional electromagnets for lift, along with linear induction or synchronous motors for propulsion. This tends to compound construction and manufacturing problems, create additional problems of reliability in regard to cooling requirements for the superconducting magnets, temperature sensitivity and demagnetization possibilities for the permanent magnets under fault conditions, and total reliance on electromagnets leading to heavy sets of electromagnets and additional costs.
Further, induction or synchronous motors used for propulsion typically utilize complex distributed windings that are spread over the guideways or tracks for mag-lev vehicles. Such distributed windings tend to have high manufacturing costs and installation requirements and costs. Moreover, since components faults in one part of the windings are propagated along extended sections of the guideways or tracks by mutual coupling with other windings, such machines are not fault-tolerant and hence unreliable for continuous operation under all conditions including that of the fault condition. Since the windings are along the track or guideway it can be difficult to locate and repair or replace failing winding components without disrupting the flow of traffic on the guideway. In order to replace the failed component, a whole section of the phase belt for all phases must be dug out and replaced. Such a whole section may be as long as a few feet to a hundred feet in a mag-lev transportation system.
In view of the foregoing considerations, improvement in electromagnetic propulsion technologies and transportation systems is called for.
This invention is, more particularly, an improvement with respect to the control system of the invention set forth in PCT Application No. PCT/US01/15208 and having International Publication No. WO 01/87663 82, published 22 Nov. 2002, of which I am a co-inventor.
The instant invention may also be viewed with respect to the broader technology of linear switched reluctance machines (“LSRM”) as employed in transportation and other translational means. Such art is reflected in U.S. Pat. No. 3,934,183 (1976) to Saufferer, entitled Linear Reluctance Motor for Rail Propulsion; U.S. Pat. No. 5,343,811 (1994) to Schuster entitled Power System for Low Friction Transportation of loads; U.S. Pat. No. 5,479,145 (1995) to Kalsi, entitled Superconducting Electromagnetic for Levitation and Propulsion of a Mag Lev Vehicle; U.S. Pat. No. 6,044,770 (2000) to Davey et al, entitled Integrated High Speed Maglev System; U.S. Pat. No. 6,439,513 (2002) to Pascoe, entitled Passive Detection System for Levitated Vehicle or Levitated Vehicle System; U.S. Pat. No. 5,722,326 (1998) to Post, entitled Magnetic Levitation System for Moving Objects; and U.S. Pat. No. 6,250,230 (2001) to Post, entitled Apparatus and Method for Reducing Inductive Coupling Between Levitation and Drive Coils within a Magnetic Propulsion System. Related foreign art includes German Patent No. 22-57-773-A (1974) to Weh. As such, mag-lev transportation and translation systems, including the above-referenced type which suggests the use of superconducting electromagnets have, in view of the considerations above set forth, proven to be less than satisfactory in terms of the technical and economic realities thereof.
A fundamental problem associated with mag-lev systems has been that of optimizing the switching and control systems associated therewith. U.S. Pat. No. 5,936,373 (1999) to Li et al, entitled Wide Pole Switched Reluctance Machine and Method of its Control; and U.S. Pat. No. 6,291,949 B1 (2001) to Greene, entitled Control of Switched Reluctance Machine, both suggest the use of polyphase switched control, however relative to a rotary, not linear, reluctance systems and, as such, are not applicable to translation systems that are the focus of the present invention.